Different vRNA segments are shown here as lines of different colors (red, green and yellow). Regions of vRNA that are not bound to nucleoprotein may form RNA structures, which mediate inter-vRNA interactions. It is also possible that vRNPs interact with each other by a still unknown mechanism, which is depicted here as a question mark. Closely related IAV strains have compatible vRNA-vRNA interaction profiles resulting in efficient genome packaging (left). For divergent IAV strains, dissimilarity in nucleotide sequences results in formation of RNA features that are not compatible for RNA-RNA interactions, and thus reduce genome packaging efficiency (right).